Sources close to Intel have confirmed that Intel believes that the SSE4 instructions will help Intel to win the battle over Barcelona K10 and Phenom. The new Penryn generation or Harpertown, Wolfdale and Yorkfield are the first CPUs to support SSE4 and Intel spent a lot of time and money to optimize at least a few codecs and some multimedia content.
This should result in a nice performance increase if you use an SSE4 CPU and benchmark it versus one that doesn’t have it.
Barcelona and the rest of the K10 generation can support some of the SSE4 instruction called SSE4a, but we've learned that these are only a few of the whole set of instructions.
Both CPUs are getting really close to launch.